1. Field of the Invention
The present invention relates to a magnetic disk apparatus for use in an information processing device, and, particularly, to a magnetic head positioner for positioning a plurality of magnetic heads mounted on a holder arm in predetermined positions corresponding to a plurality of magnetic disk media, respectively, by swinging the holder arm.
2. Description of the Related Art
Referring to FIG. 1, a conventional magnetic head positioner has a holder arm 51 on which a plurality of magnetic heads 60 for reading and writing data magnetically are mounted at one end portion thereof and swings with respect to a plurality of magnetic disk media, a shaft 52 acting as a center axis of the swinging movement of the holder arm 51, a plurality of bearings 53 and 54 interposed between the holder arm 51 and the shaft 52 for rotatably supporting the holder arm 51 and a voice coil motor 70 for generating force necessary to swing the holder arm 51.
The voice coil motor 70 has a coil 71 mounted on the other end of the holder arm 51, a magnet 72 and a yoke 73 which, together with the coil 71, constitutes a magnetic circuit for the coil 71.
However, the conventional magnetic head positioner has a following disadvantage.
Since the holder arm repeatedly swings for positioning the magnetic heads, grease filing a space between the pair of bearings may be unevenly distributed. As a result of such uneven distribution of grease, mechanical resistance is increased and considerable load is applied to the bearings interposed between the holder arm and the shaft when the holder arm is swung, causing the life of the bearings to be shortened considerably.